No invention in my lifetime has so changed an art and cheapened it as the Sony Walkman, which first infiltrated our culture 25 years ago this month.

Until its advent in July 1979, music had to be visited, like painting and sculture, in a fixed place, a gallery or living room. It could be hoiked to the beach or the park on a transistor radio (or lugged about anti-socially on a ghetto-blaster), but the listener had no choice on a tranny - no control over content, any more than he did over the pictures in an art book purchased at a station forecourt.

The Walkman, with revolutionary force, made music portable and subject to personal selection. It fulfilled the nursery-rhyme, he shall have music wherever he goes and became so ubiquitous in a short period of time, with 340 million worldwide sales, that its brandname became generic and was admitted to the Oxford English Dictionary.

Its advantages were many, mostly unforseen. Actors learned their lines by Walkman on the bus into rehearsal. Splenetic executives used it for lunchtime meditation. I once heard Mahlers Resurrection Symphony on a vertical Alpine train as a thunderstorm crashed all around. In unforgettable settings, music acquired unsuspected dimensions.

But these benefits were soon outweighed by its corrosive effects. The Walkman arose from a coincidental brainwave by Sonys three famous co founders. Masaru Ibuka, the engineer, longed to hear symphonies on long-haul flights; Akio Morita, the marketeer, wanted to get into teen wallets; Norio Ohga, the musician, sought to extend the shelf life of the incurably hissy musicassette.

Their`launch version, called Soundabout, was pitched at five cents below $200 on an unprimed US market. Lacking any kind of frills or hiss reduction, this silver-blue brickette became an instant hip accessory to the rock generation. By winter, the rebranded Walkman was pushing a million sales and spawning all manner of extras  AM/FM radio, Dolby B and C. Soon to follow were recordable machines, shirt-pocket models and a yellow Sports Walkman, supposedly water-resistant but so heavy that it was bound to drownanyone short of Olympic pool practice.

It was not only the hip and the cool who hooked on. Eminent conductors would not leave home without a Walkman Professional on which to rerun their rehearsal errors. The editor of the Sunday Times was given a Walkman as a retirement present, wrapped with a set of Shostakovich string quartets. In its first five years, before tinnier imitations swamped the stores, the Walkman was an object of pride and desire to owners and makers alike.

There was, however, a significant drawback to the ingenious machine. In early wonderment at its portability, we kidded ourselves that the Walkman made an approximately musical sound. In the cold light of retrospect, the truth is it never did. Even a Walkman Pro with noise reduction in a soundproofed room failed to reproduce anything like the dynamic range of a symphony orchestra, the high Cs of a Pavarotti, the low rumblings of a Glenn Gould. Set beside the cheapest compact disc, the best cassette Walkman was, sonically speaking, a donkey cart. The Walkman CD, its generic successor, would skip tracks when taken jogging.

Then there was the health impact. ENT specialists warned unheeded that prolonged exposure to anything above 93 decibels, could inflict irreparable hearing loss. Pop fans received 105db through Walkman headphones. Cases of deafness were reported in medical journals, as well as aural cavity damage from the insertion of mini headphones. A generations ears were physically wrecked.

Beyond hearing loss, the sonic opacity of the Walkman attacked our musical taste. Instead of seeking melody, listeners grew satisfied with crump-crump rhythm. The decline in classical concertgoing may be partly ascribed to the Walkman, which devalued magnificence and rendered its utilitarian. A Bruckner symphony buzzing away while you brush your teeth is an altogether different experience from attending a Vienna Philharmonic concert in the Musikvereinsaal.

The social pleasure of sharing music was terminated when people clamped plugs in their ears and tuned into a selfish sound. Music in the Walkman era ceased to connect us one to another. It promoted autism and isolation, with consequences yet untold.

Mercifully the Walkman is now practically obsolete in the western world(though booming in China). It has been superceded by the ingenious I-pod which packs up to 40 gigabytes of music onto a hip-slung machine and allows us to download and reload legally and at will. The sound quality is digital, hence pristine. The headphones remain inadequate and the health dangers remain but it is not beyond reason to expect that within a few years we will be able on an I-pod to reimagine Musikvereinsaal sound in the space of eighteen inches between two healthy ears.

I have not yet joined the I-pod rush but friends regularly ruin my digestion by relating how easy it is to reassemble their jazz collection, at 79 pence a track, onto their I-pod and play it back through their laptop in a hotel room in Tashkent. I sometimes ask if they know what they are missing in the transaction.

When I say context they look blank, for 25 years of Walkman usage has destroyed any sense of a piece of music having a place in the world, in time, in our personal lives. Music, made portable, is removed from any frame of reference. It becomes a utility, undeserving of more attention than drinking water from a tap.

The music industry, by making the art ubiquitious and inescapable, robbed it of our respect as a unique and precious resource. Music that tinkles from the lugholes of passengers either side of you on the Clapham omnibus is not something that will be cherished. Once consumers regard music as valueless they have no compunction in taking it for free. The music industry has no one to blame for the devaluation but itself.

The effort that goes into the creation and production of music has been obscured by the drivelling of music in all places this side of the cemetery. It takes a film like The Weeping Camel, where musicians in a Mongolian mountain vfillage are required to persuade a dromedary to succkle her newborn, to remind us that there are still places on earth where music is a rare and seldom thing, a remedy for natural disaster.

So while the moguls of Sony may celebrate the jubilee of another small step for mankind with the launch of an I-pod challenging Newtork Walkman, I shall mourn an art that was ripped from its rightful place and reduced in moral worth. The day the Walkman landed was the day the music began to die.